• 수면정신생리
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• 제21권2호
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• pp.51-60
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• 2014

A 'circadian rhythm' is a self-sustained biological rhythm (cycle) that repeats itself approximately every 24 hours. Circadian rhythms are generated by an internal clock, or pacemaker, and persist even in the absence of environmental time cues, collectively termed 'zeitgebers.' Although organisms generate circadian rhythms internally, they are entrained by environmental stimuli, particularly the light-dark cycle. Measurement of the endogenous melatonin rhythm provides relatively reliable surrogate way of assessing the timing of the internal circadian clock. Also, core body temperature and cortisol can be used as markers of circadian rhythms. The sleep-wake cycle, body temperature, and melatonin rhythm have a stable internal phase relationship in humans and other diurnal species. They play an important role in controlling daily behavioral rhythms including task performance, blood pressure, and synthesis and secretion of several hormones. In this review, we address not only the properties, methods of measurement, and markers of circadian rhythms, but also the physiological and psychological importance of human circadian rhythms.

• 한국패류학회지
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• 제15권2호
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• pp.127-131
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• 1999

전북 곰소만에 서식하는 바지락의 생리적 리듬을 알아보기 위하여 24시간 동안 1시간 간격으로 산소소비율 및 여수율의 변화를 측정하였다. 바지락의 호흡율 및 여수율에 의한 생리적 리듬은 15$^{\circ}C$와 $25^{\circ}C$에서 두 가지 모두 24시간 동안 2번의 peak를 보이는데, 밤-만조시에 최대를 나타내었으며, 낮-간조시에 최소를 나타내어 조석에 의한 일주리듬 현상을 보였다. 24시간 동안 산소소비율 및 여수율의 변화는 수온별로 급격한 특수한 변화를 보이지 않았다.

• The Journal of Korean Physical Therapy
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• 제29권3호
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• pp.142-144
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• 2017

Purpose: Few studies have addressed the effect of diurnal circadian rhythms on postural stability, and thus the aim of the present study was to examine circadian effects on static and dynamic postural stability in young adults. Methods: Twenty-four subjects (9 men, 11 women: age=$22.20{\pm}1.77$, height=$167.20{\pm}10.47$, weight=$59.85{\pm}10.66$) from a university community volunteered for this study. Static and dynamic balance testing, which recorded using a Good Balance system (Good Balance, Metitur Ltd, Finland) was conducted at 9:00, 13:00, and 17:00 hours on two consecutive days, and the sequencing of static and dynamic balance tests were randomized. Results were analyzed using the non-parametric one-way repeated Friedman test in SPSS version 18.0 (SPSS Inc., Chicago, IL, USA), and variable found to be significant were subjected to Wilcoxon post hoc testing. Results: Static and dynamic balance showed significant difference at the three times assessments (test at 9:00, 13:00, and 17:00) during circadian. In the post hoc test of static (anteroposterior distance, mediolateral distance and COP (center of pressure) velocity) and dynamic balance (performance time), 13:00 was the longer and faster than 9:00. Conclusion: These results indicated that control of postural balance is influenced by diurnal circadian rhythms, and confirm that control of postural balance is more effective and better performance in the 09:00 hours than 13:00 hours or 17:00 hours.

• Asian-Australasian Journal of Animal Sciences
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• 제10권3호
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• pp.304-307
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• 1997

Rectal temperature (Tr), skin surface temperatures (Ts), and heart rate (HR) were measured continuously from birth (day 1) till day 7, while resting heat production (HP) was measured in a chamber on days 1, 3, 5 and 7, in order to study the characteristic variation of Tr in newborn calves by heat balance methods. Despite constant levels of milk being given to the newborn calves each day, daily mean resting HP was lowest on the day of birth, then increased to peak on day 3 and then decreased slightly thereafter. Daily mean HR was higher on days 2, 3 and 4, than on other days. Tr exhibited diurnal rhythms and daily mean Tr was low on day 1, high on day 3, and then decreased slightly after day 3. Daily average mean skin temperature (mTs) was similar on all days. Mean body temperature (Tb) exhibited diurnal rhythms and had a similar range between days, suggesting that heat balance and thermoregulation were carried out effectively on each day. The variation of Tb appeared to be synchronized with that of HP and suggested that newborn calves might use variations in the levels of Tb to facilitate the body's required levels of heart loss.

• Fisheries and Aquatic Sciences
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• 제4권3호
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• pp.130-137
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• 2001

In the present study, the locomotor and feeding activities of single red sea bream, Pagrus major were simultaneously investigated to examine the existence of such dual behaviour. Seven red sea bream of 13cm body length on average were placed individually in 35L tanks equipped with an infrared sensor and a newly developed demand-feeding device. Fish were exposed to a light: dark 12: 12h cycle and constant darkness (DD) to study endogenous rhythmicity. Under LD 12: 12 h, the daily pattern of behaviour differed between individual fish; some red sea bream were diurnal and others were nocturnal. Futhermore, some of them displayed an extraordinary flexibility in phasing because they were dark active but light feeding, and vice versa. Under DD, red sea bream showed free-running rhythms for locomotor activity and feeding. These results indicate that the type of phasing of locomotor activity did not necessarily decide the feeding phase; much of this is explained by the fact that red sea bream were demand-fed. Flexibility in phasing and a certain degree of independence between locomotor and feeding activities could be seen as an adaptative response of the highly adaptable circadian rhythms of fish.

• 대한약리학회지
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• 제21권2호
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• pp.128-141
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• 1985

실험적으로 명암에 적응시킨 백서의 뇌내 specific opiate binding과 ${\beta}-endorphin$ 함량 일중변동에 미치는 지속적인 암적응, phenobarbital 장기처리의 영향을 관찰하고 opiate recptor binding과 ${\beta}-endorphin$ 함량 양자간의 관계를 추구하여 다음과 같은 성적을 얻었다. 1. L : D, 12 : 12 주기에 적응시킨 대조군에서 maximum $(^3H)$-morphine binding과 뇌내 ${\beta}-endorphin$ 함량은 각각 22시 및 06시에 최고에 달하는 매우 특이한 일중변동을 보였고 24시간 평균 $(^3H)$-morphine binding 및 뇌내 ${\beta}-endorphin$ 함량은 각각 0.45+0.03 pmol/mg protein과 46.7+3.6 fmol/mg protein이었다. 2. D : D, 12 : 12 주기에 적응시킨 표본에서 maximum $(^3H)$-morphine binding과 뇌내 ${\beta}-endorphin$ 함량은 대조군에서와는 달리 02시 및 14시에 최고에 달하는 유의한 일증변동을 보였고, 24시간 평균 maximum $(^3H)$-morphine binding치는 0.36+0.03 pmol/mg protein으로 대조군에 비하여 유의하게 감소를 하였으며, 24시간 정균 뇌내 ${\beta}-endorphin$치는 35.9+3.1 fmol/mg protein으로 대조군에 비하여 유의한 감소를 보였다. 3. Phenobarbital처리 표본에서 maximum $(^3H)$-morphine binding과 뇌내 ${\beta}-endorphin$ 함량은 각각 02시 및 14시에 최고 그리고 14시 및 02시에 최저에 달하는 대조군과는 다른 일중변동을 보였고, 24시간 평균 maximum $(^3H)$-morphine binding치는 0.33+0.03 pmol/mg protein으로 대조군에 비하여 현저한 감소를 보였다. 4. 전 실험군에서 opiate receptor binding의 Kd치는 변동하지 않았다. 5. 전 실험군에서 maximum $(^3H)$-morphine binding은 ${\beta}-endorphin$ 함량과 유의한 역상관관계가 있었다. 이상의 실험성적은 phenobarbital이 뇌내 ${\beta}-endorphin$ 함량과 opiate수용체의 숫적변동을 일으켜 morphine의 약리적 작용을 변동시킬 수 있으며, 이와 더불어 opiate 수용체와 ${\beta}-endorphin$ 함량 일중변동을 변화시킬 수 있음을 보여준다.

• Fisheries and Aquatic Sciences
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• 제4권3호
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• pp.138-143
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• 2001

Red sea bream, Pagrus major a fish species characterized by its dualistic feeding pattern, was investigated to study the synchronizing effect of light and food on the demand-feeding rhythm. Nocturnal and diurnal red sea bream, both in groups and individually, were exposed to restricted-feeding and Light-Dark cycles of different periods. The phase relationship between both zeitgebers was also studied. In some cases, food availability restricted to the light or dark phase contrary to that of the previous feeding phase changed a diurnal feeding pattern into nocturnal and vice versa, suggesting that food can be one of the switching factors that decides whether the circadian system of red sea bream is diurnal or nocturnal. However, the fact that the feeding pattern of some fish was unrelated with the phase in which food was available suggests that other internal and/or external-factors could be involved in the temporal flexibility of red sea bream.

• BMB Reports
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• 제43권7호
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• pp.506-511
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• 2010

The levels of salivary cortisol and cortisone in Korean adults were measured for the first time using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The salivary cortisol and cortisone were separated within 10 min. The regression coefficients (r) of the calibration curves were greater than 0.999 for the two steroids. The limits of quantitation (LOQ) were 0.2 ng/ml for cortisol and 1 ng/ml for cortisone. The intra-day precisions of the assay were <3.9% and 8.6% for cortisol and cortisone respectively, and the inter-day precisions were <1.9% and 4.3% for cortisol and cortisone, respectively. The salivary cortisone concentrations were approximately 4-9 times higher than those of salivary cortisol during the daytime. Diurnal rhythms, during which the cortisol and cortisone concentrations were higher in the morning than in the afternoon, were also observed. The present assay may be useful for the diagnosis of several adrenal dysfunctions in clinical biochemistry.

• Animal cells and systems
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• 제16권1호
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• pp.27-33
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• 2012

The suprachiasmatic nucleus (SCN) of the teleost hypothalamus contains a central circadian pacemaker, which adjusts circadian rhythms within the body to environmental light-dark cycles. It has been shown that exposure to darkness during the day causes phase shifts in circadian rhythms. In this study, we examined the effect of exposure to darkness on the mRNA expression levels of two circadian clock genes, namely, $Period2$ ($Per2$) and $Cryptochrome1$ ($Cry1$), and the rate-limiting enzyme in melatonin synthesis, arylalkylamine $N$-acetyltransferase-2 (Aanat2), in the pineal gland of olive flounder, $Paralichthys$ $olivaceus$. The expression of these genes showed circadian variations and was significantly higher during the dark phase. These changes may be involved in the mechanism of dark-induced phase shifts. Furthermore, this study suggests that olive flounder may be a teleost model to investigate the localization and function of circadian oscillators.

• 한국양식학회지
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• 제14권1호
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• pp.35-42
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• 2001

The larvae of the Korean bullhead, Pseudobagrus fulvidraco were satiated with the food uptake equivalent to 13% of its body weight and required 2.5, 11 and 15 hrs to digest 50, 90 and 100% of the consumed food. The juveniles were satiated with food equivalent to 0.65% of its body weight and required 9 and 19 hrs to digest 50 and 90% of the consumer. Apparently, daily food intake perceptibly decrease with the larvae grew to juvenile stage. Both larvae (8.3-14.0mm TL) and juvenile (41.1-65.7mm TL) tend to feed frequently than to get satiated once a day and appeared to be nocturnal feeders.